115hp Optimax not reaching temp

[rojorin]

Hoping someone can help me figure out what to do next. I get the single beep alarm that the engine is not reaching operating temp at idle (~140 degrees). I changed the water pump and get a good stream. I also change the water pressure sensor as I was getting readings all over the place from 0 - 29 psi and the new pressure sensor seems to have solved that issue. I changed the poppet valve, tried 2 thermostats and tested them in water to make sure the open at the ~140 degrees. I also changed the temp sensor near the top cylinder but still have the same issue of not getting above ~106 degrees at idle. What else can I do? I am getting frustrated and I am hoping I am not causing damage as the motor runs fine except for the idle temp.

Dan @ European did service my fuel rail and injectors over the winter as well and that is all doing fine. Just this idle temp has me going crazy chasing it.

Many thanks!

temp pic2.jpg

[EuropeanAM]

Responded to your PM. May be debris in the bypass/tuner cooling port (causing elevated block pressure and cycling of the poppet valve).

[rojorin]

Thanks Don for the response and PM. Posting here so others may benefit.

I am going to try and put the old poppet back in and see if that makes any difference. If not I can go down the path of pulling the powerhead. Looking in the service manual it seems fairly straight forward. It's odd that this all started after changing the poppet and thermostat as I wasn't having any issues other than I believed they were original to the motor (2007) and should be changed as regular service. But I guess something could have gotten stuck in that passage. Besides lifting ring, a way to lift the powerhead and a new gasket what else would be need for this job should I go down this road?

You suggested the below:

"There's a small bypass passage (approximately 1/8" hole) in the adapter plate that feeds water to cool the tuner and also acts as a bypass/relief for water pressure at IDLE.

If this becomes restricted or blocked- pressure will be elevated (and may cycle from 9-10 psi to nothing and back at idle). Will prevent engine from reaching temp because poppet is cycling open and closed.

I fought one for some time that kept getting run where oak "twirly-birds" would get stuck in this passage.

Bad part is you have to pull the powerhead and may have to pull the adapter plate too."

[rojorin]

Wanted to provide all an update in case anyone has the low temp issue. I was prepared to remove the powerhead and adapter plate but before I did that I figured I would replace the air pump screen and see if there was any crap in the screen. Well of course it had never been changed and was impossible to remove. It ended up snapping the head off and so I had to pick the threads with a pick and a little heat. Well after I snapped the nipple off I notice there was no screen attached to the threads. Once I replaced the screen and fired it up the temp went back to normal at idle. Up to 140-145 and then dropped back to 132-133. Glad I didn't have to pull the powerhead. Don would the screen missing cause the low temp issue? Or maybe the screen was blocked up and broke off when I was removing it and fell into the engine?